1. Field of the Invention
The present invention relates to an impact device, and more particularly to an impact device for a pneumatic tool and that has a durable structure.
2. Description of Related Art
An impact device is mounted in certain pneumatic tools to connect a tool head sleeve to a rotor in the pneumatic tool to make the sleeve rotate with the rotor in a desired direction; With reference to FIG. 5, a conventional impact device (60) for a pneumatic tool in accordance with the prior art comprises a carrier (61), two hammer pins (63), two hammers (62) and an output axle (64). The carrier (61) is connected to a rotor (65) in the pneumatic tool to rotate with the rotor (65). The hammer pins (63) extend into the carrier (61) in parallel. The hammers (62) are mounted in the carrier (61) and respectively engage with the hammer pins (63). Each respective hammer (62) has an engaging hole (not numbered) defined through the hammer (62). An impact protrusion (not numbered) is formed on the inner surface of the engaging hole in each respective hammer (62). The output axle (64) is inserted into the carrier (61) and extends through the engaging holes in the hammers (62). Two jaws (641) are formed on the output axle (64) and correspond to the impact protrusions in the engaging holes of the hammers (62).
When the rotor (65) is rotated by compressed air supplied from a pneumatic source and applied to the pneumatic tool, the carrier (61) will rotate with the rotor (65). The hammers (62) will rotate with the carrier (61) due to the engagements between the hammers (62) and the hammer pins (63). The impact protrusion in the engaging hole of one of the hammers (62) will engage with the corresponding jaw (641) on the output axle (64), and the impact protrusion in the engaging hole of the other hammer (62) will be kept from engaging with the other jaw (641) on the output axle (64). Consequently, the output axle (64) will be driven to rotate with the carrier (61) through the hammer (62) engaging with the corresponding jaw (641). A tool head sleeve (not shown) mounted on the output axle (64) will be rotated to tighten or to loosen a fastener, such as a nut or a bolt.
When the rotor (65) is rotated in a reverse direction, the output axle (64) will be driven to rotate in the revere direction through the other hammer (62) engaging with the other jaw (641) on the output axle (64).
However, only one hammer (62) engages with the jaw (641) on the output axle (64) to drive the output axle (64) to rotate in a desired direction, so only one hammer pin (63) engaging with the driving hammer (64) bears the entire load applied to or supplied from the output axle (64). The other hammer pin (63) will be kept free from loading during the operation of the impact device. The hammer pins (63) of the conventional impact device are easily broken and damaged due to the considerable loading, and the useful life of the conventional impact device is short.
With reference to FIG. 6, another conventional impact device (70) for a pneumatic tool in accordance with the prior art comprises a carrier (71), a connector (73), a hammer (72), a pivotal pin (74) and an output axle (76). The connector (73) is mounted in the carrier (71) and is connected to a rotor (75) of the pneumatic tool to rotate with the rotor (75). A notch (not numbered) is defined in the connector (73). The hammer (72) is mounted in the carrier (71) and has a semicircular cross section. A tongue (not numbered) extends from the hammer (72) and engages with the notch in the connector (73), such that the hammer (72) can rotate with the connector (73). The pivot pin (74) extends through the carrier (71) and the hammer (72) with the tongue (72) to pivotally connect the hammer (72) to the carrier (71). The output axle (76) is inserted into the carrier (71) and has a jaw (761) with a semicircular cross section to abut against the hammer (72).
When the rotor (75) is rotated by compressed air supplied from a pneumatic source and applied to the pneumatic tool, the output axle (76) will rotate with the rotor (75) through the transmission of the connector (73) and the hammer (72).
However, as the pivot pin (74) of the conventional impact device must bear the load applied to or supplied from the output axle, the pivot pin (74) is also easily broken or damaged when a large external force is applied to the output axle (76).
To overcome the shortcomings, the present invention tends to provide an impact device to mitigate or obviate the aforementioned problems.
The main objective of the invention is to provide an impact device for a pneumatic tool and having a durable structure to elongate the useful life of the impact device. The impact device has a carrier, a hammer, a pivot pin, two hammer pins and an output axle. The carrier is adapted to be connected to the rotor and has a bridge and two walls. Two depressions are defined in the top of the bridge. An elongated hole is defined each respective wall of the carrier. The hammer is pivotally mounted in the carrier between the walls through the pivot pin. Two legs respectively extend from the hammer to define a recess with an opening in the hammer. A cavity is defined in each respective leg and corresponds to one of the depressions in the bridge. An impact protrusion is formed on each respective leg to narrow the opening of the recess. The pivot pin extends through the elongated holes in the walls of the carrier and the hammer to pivotally connect the hammer to the carrier. Each hammer pin is moveably received in one of the depressions in the bridge and the corresponding cavity in the hammer. The output axle is inserted into the carrier and has a jaw longitudinally formed on the output axle and selectively abutting against one of the impact protrusions on the hammer. With such an impact device, all of the hammer pins can bear the load applied to or supplied from the output axle. The impact device has a durable structure, and the useful life of the impact device is prolonged.